(1) Field of the Invention
The present invention relates to the generation of electrical signals commensurate with sounds to be produced by a key board actuated electronic musical instrument and particularly to the production of signals which identify both the selected key and the manner in which that key has been operated. More specifically, this invention is directed to key board systems for electronic musical instruments and especially to key/transducer arrangements which provide electrical signals commensurate with the key touch dynamics. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
Electronic musical instruments, particularly those which have a key board system for the election of individual sounds to be produced, are well-known in the art. While the previously available electronic key board instruments, i.e., electronic organs, have been quite versatile, there has nevertheless been a long standing desire to enhance the ability of such instruments to simulate the sounds produced by a piano. In conventional pianos, the volume of the generated sound depends upon the force with which the player actuates the piano keys. There is significant demand for electronic organs which, insofar as the generated sound is concerned, behave like conventional pianos.
The state-of-the-art is believed to be exemplified by the article "PIEZOTASTEN SORGEN FUR PIANOEFFEKT IN ELECTRONISCHEN ORGELN" by P. Kleinschmidt, appearing at pages 1125-1126 of the 1977 issue of FUNKSCHAU. The aforementioned article describes a key system for an electronic organ wherein an arm of the key abuts a piezoelectric element and the electrical signal produced by the piezoelectric element at least in part depends upon the nature of the mechanical pulse transmitted thereto by the key.
Another example of prior art may be seen from published German Patent Application No. DE-OS 22 61 071 which discloses a key system wherein a "hammer" is displaced by the key, the displacement being a function of the mechanical pulse transmitted by the key. In the system of the published application the hammer displacement is transduced into an electrical signal by a pressure-sensitive resistor.
Capacitive key associated transducer systems are also known. In such systems the source of charging current for a capacitance is disconnected upon initial actuation of the key and the charge remaining on the capacitor, which discharges during the key stroke, is sensed at the end of the stroke. In such capacitive systems the charge remaining on the capacitor at the end of the key stroke is a function of the speed of the stroke. Such capacative systems incorrectly presume that key stroke speed is necessarily a function of the force with which the key has been actuated.